Two-position variable pitch propeller



Feb. 21, 1950 c. l. LATHREM TWO-POSITION VARIABLE PITCH PROPELLER 5 Shets-Sheet 1 Filed March 10, 1945 n RW Y 0 E T M W m N 5 T Feb. 21, 1950 r c. 1. LATHREM 2,498,110

- TWO-POSITION VARIABLE .PITCH PROPELLER Filed March 10, 1945 5 Sheets-Sheet 2 fly-2.

I RNVENTQR CHARL E5 I.- LATHREM BY I I ATTORNEY Feb. 21, 1950 c. LATHREM 2,498,110

TWO-POSITION VARIABLE PITCH PROPELLER Filed March 10, 1945 5 Sheets-Sheet 3 if 57 Q W L INVENTOR CHARLES I. LATHREM ATTORNEY Feb. 21, 1950 c. l. LATHREM TWO-POSITION VARIABLE PITCH PROPELLER 5 Sheets-Sheet 4 Fil ed March 10, 1945 INVENTOR CHARLES I. LATHREM ATTORNEY Feb. 21, 1950 C. l. LATHREM TWO-POSITION VARIABLE PITCH PROPELLER 5 Sheets-Sheet 5 Filed March 10, 1945 ATTORNEY slue nzee o Patented Feb. 21, 1950 TW -BO I N VARI-AB E rnen:

BRQPELLEB tien of Canada.

enp ee ign M r L 9% vSe i l53.5 ;!)951 e (c1. me ee-e22.

met .ettieelerl e that y e seme e2 5 me haln eebie or -exietble pit'h, R Ql2e l 2 The invention provides propellers which mag lpe edi-ueteel, It e ereit at e; p esleeermine Bi h e :9 pera e a a p edeterm ned. ee ree n t'ennell seq ei ex reizetien; rienkwdre ie r e ki n-the hu -L By m ans oit hl P11 1 19; wh h e.

hen ee i ecl mere; n;- xeepen e; eenre e on elf tee preeell r. th 1 .d. i eeeseq he: eet. en y eme met w F1..1J1Z1 This meier has a P ston sl d-ab, A, ela ie e s eeEe-Wmem the: mel elie e the eneieebdewei hem By enee e um e.- weights mounted on thevb the b ades may bx me n Qith i tee. e ee ew ie me bee m me n th eee ie l bledee e e te el; t

.Q e ble lee eh 2 new lene'im m e. en eg? eleletetvopser men ed f e..re. e .nme, le le predetermined-finepitch EGSiti wh tlgi e pigjggn le heel ifuneee the eelie Pxee:

s ne in a direction opposed to tiaefeie f we L15} ewe-na midmfimeim es 5- 212einmiehee Qf thev counterwei nts! Although the novel matures," which, are .,.b.e,- lieved-to. bexeharacteristie of the inventionwill .beparticularly pointed out in the claims appended hereto, the invention itself, as-t oits objects and advantages, and-the manner; in whieh it m y be er ed m b e eer en e ees his: nventi n, elet s t air lane; repeilexs pew-mama 2 Eisz-ieeahv ew tnel prep llen ine 21-4 E. is a NEW seet en, en 23:3. 924 151 1.; Fig; 4 is a view on line, IL l gj Fig, 1 :5 Big; 5 en ine t F g; la

Bi -n fiee e fine iew i th pump u it 33%? he. le zeexu eele;

' z -ele eia ee .91? th gum? t n sep The ek em," .1..

eierr le: 193 wellp c P 8,, angle been? n '5' flare. 51 which extend legume M m e' zee fie meierrulelike ie k lve e d e e this meemefl 'Eheie e le. H. i mom i .x eel meeppe ifie. diree en ime; may I in s'zz and 23 in peeeqxele lee vsexveent F se; the flml fi,v he nmellez is. rete e ab I x th eded 9 ,351

he hellew 13x 1! i ert me ntee ,v r hqlzexete neln ite e x .1 1,315 by weldi g; ineee xelei eyunixieel eneiz and has a bore M which may be tapered slightly from the rear (that is, the end nearest the engine) toward the front end. Its interior surface has splines 34 and grooves 35 which register with corresponding splines and grooves on the exterior surface of the drive shaft. The drive shaft I3 has a bore 36.

The inner end of hub insert I2 is flared and the flared portion 31 has a tapered interior surface 38. The outer end of the insert also has a flared portion 39 having a tapered interior surface 40 tapering inwardly toward the rear. When the propeller is mounted on the engine drive shaft I3 a spacer ring 42 abuts the shaft nut 3. A rear cone ring 43 abuts the spacer 42, and the interior surface 38 of the insert flared portion 31 engages the exterior tapered surface 44 of the cone ring 43. A split front cone ring 45 fitting around the forward end of the drive shaft I3 has a tapered surface 46 engaging the interior tapered surface 40 of the'insert'flared portion 39. This split cone ring 45 has an outwardly extending cylindrical wall portion '41, having an annular groove 48.

To secure the propeller to the drive shaft I3 there is provided an internally threaded shaft nut 49, the threads of which engage corresponding external threads on the shaft. An annular flange 50 on the nut 49 fits into groove 48.

Hence, when the nut 49 is tightened and adjusted the propeller is made fast to the engine shaft. When the propeller is thus made fast to the shaft, a shaft nut'pin 53 extending through registering apertures in the shaft nut and engine shaft prevent the nut from turning on the shaft,

thus to maintain the propeller properly secured to the engine drive shaft, notwithstanding vibrational or other forces which may tend to rotate the nut on the shaft.

The exterior cylindrical surface of the hub in- .sert I2 is provided with spaced annular flanges or bosses 60 and BI, the boss 60 for convenience ,of description being designated as the front boss,

and boss BI, as the rear boss. At their outer peripheries these annular bosses have machined or smooth surfaces 62 and 63." Each boss on 'the inside is hollowed out to provide in effect annular spaces 64 and I55. The peripheral exterior surface 66 of the insert between the spaced bosses 69 and GI is also machined or smooth. A split ring piston, designated generally by reference character 61, comprises two complementary half 'sections each of similar construction. When assembled on the insert, the piston may be said to comprise an annular piston which is an inwardly extending portion 68 within a sleeve 69. The annular or ring piston 68 engages the exterior surface 66. of the insert and the sleeve which is machined or smooth and engages the peripheral surfaces 62 and 63 of the annular bosses 60 and GI. The piston 61 is slidable co- .axially along the insert I2.

ternally threaded and ha n the opposite side,

a lug 74 having an internal bore l5. Half section Ila. issimilar and has corresponding but complementary bosses and 'bores. When fitted together in complementary fashion around the insert with the sleeve 69 of the piston 61 engaging the outer surfaces of the annular bosses '60 hereinafter.

portion 69 of piston 61 has an interior surface lever.

and til, the bore 13 registers with bore 15a and bore I5 with bore 13a. Pins "I6 and 76a each having a threaded end, a nut portion and also a projecting slot-engaging portion, secure the two half sections 'II and i la together. As shown in Fig. 2 pin I3 is externally threaded at one end to engage the threads of lug 12a. An integral nut ll provides a convenient means to tighten the pin. The outer end of the pin has a slot-engaging portion 18 disposed within the slot 19 of lever 80, described in further detail Pin 16a is of similar construction and corresponding parts are designated by the same reference characters with the sub-letter a.

The annular piston portion 68, which may be referred to for convenience of description as a ring piston, comprising the two half sections, is provided with an annular groove BI to accommodate a packing ring 82. The packing ring may be held snugly against the cylindrical surface 66 by means of a helical spring 83 within the groove and extending around the packing ring.

Boss 60 is provided with a port 84 connecting with the interior annular space 64 and boss IiI is provided with a port 86 connecting with the interior of annular space 65. As described in further detail hereinafter, hydraulic fluid under pressure may be routed through the port'84 to move the ring piston 68 coaxially in a rearward direction between the bosses 60 and BI; the port together with exterior surface 66 of the insert and the annular bosses 60 and BI provide a single acting hydraulic motor adapted to move the piston 67 in a rearward direction. The motor may be operated by hydraulic pressure, and means are provided to move the piston 61 in the opposite or forward direction, as described in further detail hereinafter.

As mentioned above, pin projection 18 engages a slot I9 in lever and pin projection 18a engages a corresponding slot 79a in lever 80a. Lever 80 comprises an arm 81 which engagesbase I9 of the ferrule I7 and is securely attached thereto near the periphery of the ferrule base by means of lag bolts 88; dowels 90 serving to align the lever with the ferrule. Fixed to the arm 81 is an angle arm 9| having, in its outwardly extending portion, a slot I9 which accommodates the pin projection 78. With moreparticular reference to Figs. 2 and 3, it will be observed that when the piston 61 is moved coaxially along the insert, the pin projection also moves coaxially. When moved toward the rear under the influence of hydraulic pressure the piston movement is translated to the lever since the pin engages it in the slot 79. However, the other arm Bl of the .lever 80, being fixed to the base of the ferrule,

the coaxial rearward movement, of the piston 61 is translated to rotary motion through the Thus a torque is exerted to rotate the ferrule I7, and hence the propeller blade I I, about its longitudinal axis. Blade Ila is also rotatable about its longitudinal axis in similar fashion by the lever Bda when piston 51 is moved rearwardly under the influence of hydraulic pressure in annular space 64.

As mentioned,v hydraulic pressure exerted in annular chamber 64 will drive the piston 67 rearwardly. The movement will be within'the'limits ammo:

ooax-i'al movement as definedi'byi the? an? nular bossesfilfand- 61 In: ordento providesforca to: move: the: piston: from its" rearwardi position its: forward position andi at: thevsamer' time to rotate the propeller blades about their'longie tudinal axes in the. opposit'e angulardirection fnomzthat caused=by=the torque exerted on them when: the piston: is: drivem by hydraulic: pressure;;, eounterweights 9 9 and 9 9a aremountedi. om the ferrules. I21. and-11m 'llhese weights are-herein. called; counterweights for convenience: oti d'es'e fgnation" Their. purposeiwill:beaunderstood from thwpreceding and; following desoriptionz.

Theicounterwieight'siare mounted irrisuohgfashe i'omthat; upon rotation. of; the 1 propeller: about its axis 28, centrifugal; iorce causesiathe weightss exert? a. torqueinn 2: direction: tot rotates" the mopellerv blades in.v a.-given; angular direetionv about-ztheir: respective longitudinal: axes Im the: illustrative embodiment diSCIO'SEdxiH-i' the drama. lngszthe weights-@991 andr99azaremountedztoexertt mtorque opposed to the torque resulting; from thatccausedvby; the piston 61 when. the latterrris under: the influence of hydraulic :pressure: exerted, on thepiston; As shown in the drawings'zthe' eounterweights; 99; and; 99m. are: mounted: on} the ierrul'ee l-Jaand; km by meansof clamps ringsgand are soiposition'ed that uponzrotation of theproe peller about its axis 28 (clockwise asyi'ewedzfrom the}, engine) the torque exerted: by; the counterweights: is :irra. direction to: rotate the propeller? bladesal I; and: Ma aboutwtheir"longitudinaltaxes toward coarse, pitch, position. and. at.- the; same: time levers 80-. and. 80a. .move thering piston? 68! to-itsiorward position. Correlatively, hydraulic. pressure, in. annular: space; 6.4. upon. ring; piston-,- fiitsets upnaztorque through.levers;-80,andi8lla in aadirection to rotatethe blades M: and Ma to ward; fine pitch. position The; means for. estabr' lisliing" and.v relieving. hydraulic: pressure: in the annular space 64; is. described in: further; deta l; hereinafter.

; Referring'again to. the counterweightsfiflwfandi 9912;; they: are mounted on: the. ferrulesibyi clamp; m'n'gst. 92: and 92a. A stop arrangement'i-pro'a widedtooontrol: the adjustments of-the-propell'eu bladee with-in predetermined limits: for" fine on COEISG'FDitCh DOSitiOI-IS; This 'a'rrangement for propell'er blade I l comprises split clamp? ring: 92 clamped to ferrule IT and a lug? St'rZlSeCurBdftQwtM-n periphery of-rthe hollow arm I 6 of thezhub I l A: similar arrangement ispnovidedfonblade lsl'unthe corresponding parts; being designated I bysimilar neferencercharacters. withsub ;-letters-z"d.i"" 1 A typicalclampring; comprisessaisection; 4; having" lugs 55 and. 9.9: and; a halfi section-i 59 having 1ugsa94r andil': Itwillz be observed that half section: 5.6; carrieszas: an. extension of 1113' ili' the= counterweight 99. extending. in: substan:- tially radial directionfrom: the. ferrule anctlit' Should be observed; that the center of gravity. of thetoounterweightr 99: for: blade; LLliesitopone side of the: plane of rotation; of i the: propellemindia catedzbythe dot-dash lineri59 in'Eig; 5. Itwi'llzbe further observed: that the center. of gravitsr of: counterweight. sea for. blade Ila lies toione side of the: plane of? rotation of the propeller-rand:- positioned-L relative to weight: 99 to; give: balance betweenthe two.propellerblades l I; and Ho;

-' Thus, the arrangement. is. such that-the (rem. ters: of gravity of two counterweightsi are, lo. cated sothat uponwrotation of thepropellen about itsmxisrZSrin: aficlockwise directionas viewedif B01112 thersengine, the weights; 99; and; 99a. willitendi-itu toll'oweim a. circular. pathtinsa .planeethrough;

iii

longitudinal axes fl'iiendi zlia ofethezblades', which. plat-wise perpendicular: to; the. propeller: axis: .28; Consequently; the: weights: will; exert a torque to; rotate: the blades: angularlwom their long-1; axes. towardcoarseipitcir; position. It; may; be obisewewalsqithagt the weights, could; if. desired-the; adjusted ta exertza torquexim the oppositean l gular direction towardi'fineapitchi But-;for. pure posesg of: displosure: it; is deemed; sufficient: to confine: the, description; to the; embodiment; shown wherein the weights .99. and; 99aflnormally= maintains the, blades; in. coarse; pitch when the, propellen is rotatingat; its: normal speed.

'Iihealugs 99; andrfld' aremaintainedringpredeter; minedxfixed spacedz relation bygthe; bolts9l andp58 which. alsmserye. to secure-the clamp rings-rte the: fer-rule I611: The": outwardl extending lu s: 931 and): 94 also:- provide stops;- which, may bead: 11 6 for finer and. coarse pitch positions and cooperate; thev lug. 955011 the hub.v It; willbe understood}. of? course; that. clamp-ring; Maris; similarly; constructed. and; the corresponding parts: are: designated? by;- similar: referen ce char.- acters having the sub-letter a.

Thus, when: the; stops" are properly adjusted and; assuming the=-propel1en is, rotating inclockr, wise-direction: as-viewedv insFig; 2, the stop 914i will? engage lug; 95 when there is no hydrauliepressure in; annular space; Elk and; the piston;- 6,7; is; urged. to. its forward. position on, the, insert throu'gh thelever mechanism 8H:v Likewise stop; 94a will: engage.- lugi 95a; In:- this: position the propeller blades are adjusted-v for: coarse pitch; which. isiitheirnormal operating: position, when the; propeller is. rotating; On; the; other hand, when?suflioienthydraulic pressure is' exerted in spa-caulk againstalring; piston. 68 to, overcome the opposing force of the. counterweights 9,9 and" 99m the-piston isgdl'iVBn; to its rearwardmosition and thezpropel-lenblades are rotated in the opposite directioneaboutgtheir: longitudinaI axes; until stop 93 engages lug 95 and stop 93a engages 1ug 9.5;w.

vvl'ii'rlr is; the; fine pitch position (see; Figs 2 and 592;

anismse. ID'Si'and the other; clamped'by screws- 1 ttoutlue-tfirst; prqvidingwachamber I95 to accome modate the rotor M21; The. p mp I09. isshaped to:bezmountedswithinzthe hub without interfering-gwithithezoperation ofthe. piston 6:1. ltmay be secured to: the: interior surface; of the; hub by meansgoi-gscrewsa; I118. The rotor H11 is-mounted eecentric'ally? to: be rotated. in therotorchamber 196-: Itmamhaveeradiallydisposed:slidable vanes- H19. Asstatedbefore; the hub chamber 85.. pro..- vides a reservoir for: hydraulic fluid; oil.- having been found preferable fon'the desired. purpose,

When; the, rotor shaft. lzl D is? rotated in proper direotiorhv the; pump takessuction. through; port from-:thereservoir provided by. hub; chamber 95;. The oil travels:v through. intake conduit; I M, then: through the rotor. chamber. 10 6; and is, dis charged under; pressure; through: discharge con d'uit, lzl Laud: then:v through discharge. port; IM:

awed-1 with grooves H3 and I I4 at the outlet and'intake ports of the chamber I06. The p'ump discharge port I04 is connected by conduit H5 to port 84 of the hydraulic motor :(see Fig. 3). Conse-,

quently, fluid pressure from the pump I may be exerted in annular space 64 to drive the piston 61 in a rearward direction.

To prevent building up of excess pressure on the discharge side of the pump, a relief valve H8 is provided in the block IOI. It will beapparent that by suitable selection and adjustment of spring H9, pressure in conduit H2 above a predetermined amount will move the valve plug H8 out from its seat and relieve the fluid pressure through relief vent I2I. The valve .plug H8 is yieldably held in its seat by the spring H9 which in turn is held by a cap I22, keptin place by a split ring I23. Thus means are provided, when the pump is operating, to maintain a substantially constant fluid pressure on the discharge side of the pump and in the conduit H leading to the annular space 64 of the hydraulic motor.

The pump I00 is operated by means'of a drive shaft I connected to the rotor shaft H0 by a coupling I20. Drive shaft I25 passes through a housing I21 which extends outwardly through the wall of hub barrel I5 (see Figs. 3, 5 and 9).. The shaft I25 is mounted for rotation in bearings I28 and I29 mounted in the housing I21. Bearing I28 rests against an annular flange I30 maintained in place by split ring l3I and bearing I29 rests against an annular shoulder I32 and is held in place by split ring I33. To provide a seal against hydraulic fluid leaking out of the hub chamber 85, a packing ring I34 is mounted on the shaft I25 between holding rings I35 and I36. A helical spring I31 resting against a ring I3'Ib and packer holding ring I35 urges the ring I 35 against the packing I34 to insure a leak proof seal.

A friction wheel I38 is secured to shaft I25 by a nut I39 and is keyed to the shaft by a key I40.

The friction wheel has a rim having an annular friction face MI and the cup I43 within the rim provides space to accommodate the nut I39.

To cause the friction wheel I38 to rotate and consequently to drive the pump I00, there is pro vided a ring I having annular contact face I5I, mounted on hub sleeve I52 for axial movement. The hub sleeve I52 extends from a fixed plate I52b bolted to bracket I4. The bore of ring I50 is provided with helical grooves I53, of which there are three'equally spaced circumferentially. Keys I54, of which there are three equally spaced circumferentially about the hub sleeve I52, register with the respective grooves. Consequently, upon rotation of ring I50 on the hub I52, the ring I50 is caused to move axially on the hub. A cord I55 in an external groove I56 and fastened by a bolt I51, may be used to rotate the ring I50 from a remote place; :as, for example, from the cockpit of the airplane. When the ring I50 is rotated in proper direction it may be caused to move axially toward the propeller hub andthe contact face- I5I will then engage the friction face I4I of the wheel I38. With the propeller rotating, the wheel- I38 then will revolve in contact with face I5I in planet fashion, rotating wheel I38 to cause the pump to operate and build up pressure in conduit H5, sufl'icient force being established to drive the piston 61 to its rearward position against the opforce of the weights 99 and 9941. It .will

lit

be clear from the description that with rotation of the blades upon their long axes there is a corresponding axial movement of piston 61- through the connecting levers and 80a, and vice versa. a

When the ring I50 is rotated in the opposite direction it will be retracted axially along the hub sleeve I52, and the ring may be moved toward the engine sufficiently to disengage the con-- tact face I5I of ring I50 from friction face I4I of the ;wheel I38 and then the pump I00 will remain at rest. Hydraulic pressure in space .64 of the hydraulic motor will then be released back through the pump. To charge hydraulic fluid to the hub chamber 85, charging ports I60, closed by removable screws I0 I,are provided.

The operation of the device described in the foregoing is as follows: It may be assumed that the propeller assembly has been mounted on the engine as shown in the drawings. It may also be assumed that the hub barrel chamber is charged with a suitable oil of lubricating character. Also, it will have been observed that the parts have been sealed with packing material where needed and the parts otherwise joined in such fashion as to prevent oil from leaking from the propeller hub. It may be further assumed the propeller is designed for clockwise rotation as viewed from the engine.

The propeller blades II and Ha. are adjusted to the desired coarse pitch position and the clamping rings 92 and 92a are clamped to the ferrules in such manner that at coarse pitch position stop 94 engages lug 95 and stop 94a engages lug 95a. When in this position levers 80 and 80a are in such position that the piston 01 will be in its forward position. When the piston, levers and stops are in this position the propeller is adjusted for coarse pitch position and this will be the normaloperating pitch position whenthe propeller is rotating with friction wheel I38 out of contact with ring I59. That is, ring I50 will bei-n its rearward position. Assuming that the propeller is rotating with the engine drive shaft vin clockwise direction, viewed from the engine,-

the' friction wheel I38 is revolving about engine drive shaft axis 28 but is not rotating on its own axis because it is out of contact with ring I50. Also, under this set of conditions there will be no substantial hydraulic pressure in annular space 64 of the hydraulic motor because the pump is at rest,v that is. the rotor is not rotating on its axis although the pump I00 is revolving about the axis 28 of the propeller. Pressure in space 64 will have been relieved back through the pump. -.As

thepropeller rotates upon its axis 28, the centrifugal force of the counterweights rotating with the blades will maintain the blades in coarse pitch position with stops 94 and 94a engaging their respective lugs 95 and 95a. 1

If it is desired to adjust the propeller blades to line pitch position, contact ring I50 is rotated in proper direction to cause it to be moved axially toward the propeller to bring contact face I5I into engagement with friction face I4I of wheel I38. When the propeller is rotating, this causes the wheel I38 to rotate on its own axis while it is revolving around the propeller axis 28, thus causing pump I00 to operate. Operation of pump I00 will cause it to take suction through port: I03 from the reservoir of oil provided in hub. chamber and build up hydraulic pressure in conduit H5. Thus, fluid pressureis exerted in annular chamber 84 of the hydraulic 75 motor against ring piston 68, which drives .the

,pi'ston -6'| to ,its rearward pos-ition against the -.-re sultant.--torce=of weights99 and 99a and the centri-fugal twisting momentszof the blades 1- I and 11a. When pistn 151 is thus urged to its rearvward ;position,.levers :80 and 80a rotate their re- :spective ferrules I1 and Ha until stops =93 and 93a engage their respective lugs 95-and 950.. In this .qp'osition the blades are in their fine pitch position. =:I;t will :be understood of-course, that the stops 93, 93a and 94, 94a of clamp rings 92 and :92a will have been adjusted to correspond with the predetermined coarse and fine pitch positions. .It will also be observed that the distance between *stops 93 "and 9 and between 93a and 94a may *be adjusted as desired iorthe limits'of'fine-pitch I mnd coarse pitch positions.

-So long as the pump is maintained in opera 'tion, the ring piston 68 will be maintained in its rearward position and the propeller blades maintained in fine pitch position. Relief valve 8 of 1the.' pump l-zllll will prevent an excess pressure on thepiston and will maintaina substantially con- 'stant pressureinzconduit I I5.

If it is desired to return the'propeller blades iftO -coarse pitch position,ring I50 is rotatedtto move it axially on hub sleeve I52 toward the iengin'elto disengage contact face 15! from fricitioni'ace 'l4l of pump wheel I38. When so disen'gaged 'theipump llln'will'be at rest and the hydraulic pressure in annular chamber 64 of the hydraulic motor is relieved back through the pump. with no pressure exerted on the ring piston 68, the counterweights will then set up sufficient "force to rotate the propeller blades H and Ila back to coarse pitch position and the levers 80 and *BOa will return the piston 61 toits forward'posi- 'tion which corresponds tocoarsepitch position of thepropellerblades. The rotating propeller'w'ill th'enbe maintained in coarse pitch solongas'the pump I00 remains at rest.

:From "the foregoing itwill be seen that-the invention "provides a controllable pitch propeller which lsreadily adjustable for operation in two -positions,.namely, fine orcoarse pitch. The byrdraulic mechanism, comprising fluid pump, iconduits. and hydraul c motor. as well as the hy- "draulic fluid are all within 'the 'hub -and therefore --it may be said that the hydraulic operating ir'nechanism is self-contained. The counter- "weights are easily attached'to th'e'blades and may fbe re'adily adjusted. While the invention 'is -"-adapted for large "or 'small propellers, it lends cltself particularly to the construction of smaller propellers. Inasmuch as thehydraulic operat- -ing" parts azeself-contaihed within the hub,'no "fluid connections are required for connection with "butside pumps. Consequently, the propeller may be"rernoved from the engine and "replaced with dispatch and faci ity. Moreover the pump and hydraulic motor need be operated only at such times as fine pitch'adiustment-is idesired.

Although the inventionhas been illustratedan'd described with particular reference to :theiembodiment shown in the drawings it will be'understoodthat various changes, substitutions, modifications or omissions or parts may be made by 'fthose skilled :in the art without departing from the invention comprehended by the following "[claims. It will, for "example, be apparentifrom 'fthetoregoing description that the .counterweights iz'lnaybe adjusted to maintain.the propellerxblades rnormally ifin fin'e "pitch position when the 1pm- "qpeile'i' 2 is rotating r and the pump ?is at :"rest, "the iipump :being :caused to operate the :pistonrin ta Jdirectionaopposed to the sjcounterweights :tosmovei.

-10 and maintain the blades in-coarse pitch position. Audit will i also :be apparent that conduit 1 1.5 may be connected to port 86 instead of .port-fi ll-if con- .placementof said blades in a-given direction when said propeller-is rotated, .a split ring .olampedzto .eachof sa-i'd ferrules and-securing a :oounte1= weight to'athe blade, said split-rings'eachhaving Opposing lugs adjustable away from-and toward each-othenwneof saidopposing lugs engaging one of said stop lugs when the blade is in coarse ,pitch :position and the other of 'said ppposing lugs engaging that stop lug when the :bladeis in -fine;pitch position, thereby providing means .for limiting a-ngulardisplacement 10f the-blades,

Ya hollow insert .mounted :in said a hub --d-isposed at right-angles to said radiallyextending arms z for -mou-ntingsaid hub on the engine rdriveshaft, a

piston member within said hu'band mounteduon :thG'Y-SXlJEIiOI 10f said .insert for.-slidable movement thereon, a :pump mounted within said :hub, means operative upon rotation .01 :said hub to drive said pump and thereby .to cause-the pumpto force din-id pressure against said piston-to move thefpiston in one direction, and meansconne'cting'said piston with each propeller =-blade operative .in .response to movement of said piston toangularly displace the propeller blades about their respective longitudinal axes, said -,pis-ton acting toan'g-u- -larly-=displace said-blades in one direction: against the rfOICG of saidecounterweights'--When=;said fluid i-pressure lie-exerted onsaid piston; andsaid counterweights acting to angularlyidisplace saidblades in the oppos-ite' direction when said fluid pressure .is released.

2.. anrairplane propeller which comprises propeller bladea -a z'hollowihub barrel providing a reservoir; for: hydraulic fluid and. having a plu- -rality :oi radially disposed hollow arms, 'anaoutwardly ipmtrudingstop lug onaeach of said arms, means including a ferrule supporting a root :end .of 'ablade ineach ofsaidvarms for angulardis- "placement "about the :longitudinal axis of the =blade,-a A-splitring clamped .to each ferrule a "counterweight attached toeachof-said (split rings the counterweights are :mounted to. urge the blades in .a given-angular direction .upon rotation of said propeller, opposin'g lugs on each pf :the-splitring-s andadiustable towardand away from each other *and limiting the ang ular dis placement rofvsaid blades by engagement-with said -stop lugs-on said .arrns,. a hollow :insert mounted insaid hub: barrel disposed-atright anglesto said radially extending arms formounting said hub on the engine idriveshaftispaced annular bosses around the exterior of said insert, a piston member mounted--..on the exterior of .said .insert for -s-l-idable oOaQxi-altnovement between :said bosses, mounted within said hub, means on ota-tionrofesaid hub to drive said tpump, 12a conduit connecting said pump with the space :between one of -.-said bosses and piston cto carry fluid pressure from said pump to said space to move said piston, and lever means connecting said piston and blades to rotate said blades about their longitudinal axesin the opposite angular direction against the force of said counterweights when said piston is moved by said fluid pressure. 3. An airplane propeller which comprises propeller blades, a hollow hub barrel providing a reservoir for hydraulic fluid and having a plu rality of radially disposed hollowarms, stop members on said arms, means for supporting a root end of a blade in each of said arms for angular displacement about the longitudinal axis of the blade, a counterweight attached to the root end of each blade which counterweights are mounted to urge the blades ina given angular direction upon rotation of said propeller, a hollow insert mounted in said hub barrel disposed at right angles to said radially extending arms for mounting said hub on the engine driveshaft, an hydraulic motor within said hub, a fluid pump mounted within said hub, means operative upon rotation of said propeller to drive said pump and thereby to build up fluid pressure, means including a conduit within said hub barrel to carry said fluid pressure from said pump to said motor, an adjustable spring actuated relief valve means associated with said pump to maintain a substantially constant pressure in said conduit when said pump is in operation, lever means connecting said motor and blades, said motor acting to rotate said blades in the opposite angular direction from said given direction against the force of said counterweights when said fluid pressure is exerted on said motor, and lugs connected to said counterweights engageable with said stop members providing means for limiting fine and coarse pitch of the blades.

4. A variable pitch propeller for airplanes which comprises propeller blades, a hollow hub providing a reservoir for hydraulic fluid and having radially extending arms, each arm supporting a propeller blade mounted for angular displacement about its longitudinal axis, whereby the pitch of said blade may be changed, a counterweight secured to each blade and mounted to urge its attached blade toward coarse pitch position, a rotary pump mounted within said hub for pumping hydraulic fluid contained in said reservoir, an hydraulic motor within said hub operative in response to fluid pressure exerted by said pump, pitch-changing levers within said hub connecting said motor and blades and operated by said motor to angularly displace said blades toward fine pitch position against the force of said counterweights, stop means to limit the angular displacement of said propeller" blades within predetermined flne and coarse pitch positions, a hollow' insert mounted in said hub to receive the driveshaft of an airplane engine for driving connection there-' to, a pump drive shaft, means including a friction whee1 connected to said pump driveshaft and a contact plate mounted independently of said hub to drive said pump in response to rotation of said hub; and means for moving'said plate into and out of engagement with said wheel, said rotary pump, motor, pitch-changing levers and fluid all being self-contained within the interior of said hub.

5. In a changeable pitch propeller, propeller blades, a hub having arms mounting the root ends of the propeller blades for rotation of said blades about their long axes, stop members on said arms, counterweights'secured to said root ends mounted to urge said blades ina given an.-

gular direction to a predetermined pitch position, clamp rings securing said counterweights to the root ends of said blades, said clamp rings being angularly adjustable about the long axes of said blades, lugs on said rings providing ad'- justable means to engage said stop members to control the pitch limits of said blades, a hollow insert mounted in said hub for connecting the hub to the driveshaft of an engine, an annular bosson the exterior of said insert, an hydraulic motor within said hub, said motor comprising a piston engaging the exterior surface of said insert and slidable coaxially along the exterior of said insert in contact with said boss, means including levers connecting said piston and the roots of said blades to rotate said blades in the opposite direction against the force of said counterweights whereby to change the pitch of said blades to another predetermined pitch position in response to coaxial movement of said piston, a pump within said hub and having a rotatable shaft extending to the outside of said hub for producing fluid pressure, a conduit connectedwith said pump and motor whereby to' cause fluid pumped by said pump to exert pressure on one side of said piston to cause'said levers to move said blades in said opposite direction against the force of said counterweights, and means on the exterior of said hubfor connection to said shaft to cause its rotation and thereby driving said pump. a

6. A variable pitch propeller assembly which comprises propeller blades, a hollow hub having radially extending hollow arms; means mounting a propeller 'blade in each of said arms for rotation of the blade about its longitudinal axis to provide for change of the pitch of saidblades; stop means for limiting angular displacement of said blades about their longitudinal axes; a hollow insert mounted in said hub to receive the drive shaft of an engine; an hydraulic motor within said hub; a fluid pump within said hub, said hollow hub providing a reservoir for fluid to be circulated by said pump; a conduit connecting said pump and motor; means causing said pump to operate when said hub is rotated by-the engine shaft, thereby to cause said pump to exert fluid pressure on said motor; means including levers within said hub connecting said motor and blades to change the pitch of said blades in response to operation of said motor; said pump operating means comprising a friction wheel operatively connected to said pump; and a wheel, said friction wheel operating said pump when said propeller is rotated and said wheel is in contact with said contact member. 60

7. A variable pitch propeller assembly which comprises propeller blades, a hollow hub having radially extending hollow arms, means mounting a propeller blade in each of said arms for rotation about its longitudinal axis to provide for change of the pitch of said blades, pitch limit stop means for limiting the angular displacement of said blades about their longitudinal axes, a hollow insert mounted in said hub to receive the drive shaft of an airplane engine, an hydraulic motor including an annular piston in contact with the'exterior surface of said insert slidable coaxially back" and forth thereon, a roa friction wheel mounted on said pump drive shaft, a contact ring, means mounting said ring concentrically about said engine drive shaft, said ring being rotatable and movable axially to make and. break contact with said friction wheel, said pump being operated by said Wheel when it contacts said ring and at rest when said wheel is out of contact with said ring, levers connecting said hydraulic motor and the ends of said blades, said motor acting to move said levers to rotate said blades to a predetermined pitch position in response to operation of said pump.

8. In a variable pitch propeller assembly, a hollow hub having radially extending hollow arms, propeller blades, means mounting a propeller blade in each of said arms for rotation about its longitudinal axis to provide for change of the pitch of said blades, stop means for limit ing the angular displacement of said blades about their longitudinal axes, a hollow insert mounted in said hub to receive the drive shaft of an engine, an hydraulic motor within said hub, a fluid pump within said hub, said hollow hub providing a reservoir for fluid to be circulated by said pump, means including a friction wheel to operate said pump when said hub is rotated by the engine shaft, thereby to cause said pump to exert fluid pressure on said motor, means within said hub connecting said motor and blades to change the pitch of said blades in response to fluid pressure exerted on said motor, a hub sleeve mounted 3 14 independentlyof said propeller hub, and a rotatable contact ring mounted on said hub sleeve and movable coaxially along said drive shaft to make contact with said friction wheel, said friction wheel causing said pump to operate when in contact with said contact ring.

' CHARLES I. LATI-IREM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,723,617 Hele-Shaw et a1. Aug. 6, 1929 1,833,843 Leparmentier Nov. 24, 1931 1,851,874 Seppeler Mar. 29, 1932 1,894,048 Lilley Jan, 10, 1933 2,032,254 Caldwell Feb. 25, 1936 2,032,255 Caldwell Feb. 25, 1936 2,229,058 Dicks Jan. 21, 1941 2,233,468 Barthel et al. Mar. 4, 1941 2,237,191 Mills Apr. 1, 1941 2,274,334 Keller Feb. 24, 1942' 2,276,347 Ruths et a1. Mar. 17, 1942 FOREIGN PATENTS Number Country Date 346,344 Great Britain April 1931 635,992 Germany Aug. :30, 1934 782,129

France May 28, 1935 

